Magnetic field estimates for accreting neutron stars in massive binary systems and models of magnetic field decay

Chashkina, Anna; Попов, С. Б.

doi:10.1016/j.newast.2012.01.004

Cited by 36 publications

(42 citation statements)

References 50 publications

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“…We note that a statistical analysis of long-period X-ray pulsars with Be-components in SMC by [33] also favored the rotation law ω ∼ R −2 . The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere.…”

Section: Discussionmentioning

confidence: 61%

“…The dependence of f (u) on the accretion rateṀ in the case of a settling shell taking cooling into account will be derived below (see (33) below). In the supersonic (Bondi) regime we obviously have f (u) = 1.…”

Section: The Alfvén Surfacementioning

confidence: 99%

“…The capture radius can also be reduced due to radiative heating of the stellar wind by the X-rays from the neutron star (see below). To derive numerical values of the coefficients in Equations (63) and (64), we used the expressions for the coefficient Z (57) using (33) and (31) for the Alfvén radius. Below we will study the case Z − z > 0, i.e.…”

Section: Spin-up and Spin-down Of X-ray Pulsarsmentioning

confidence: 99%

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Quasispherical subsonic accretion in X-ray pulsars

Шакура¹,

Постнов²,

Kochetkova³

et al. 2013

Phys.-Usp.

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This work considers a theoretical model for quasi-spherical subsonic accretion onto slowly rotating magnetized neutron stars. In this regime the accreting matter settles down subsonically onto the rotating magnetosphere, forming an extended quasi-static shell. The shell mediates the angular momentum transfer to/from the rotating neutron star magnetosphere by large-scale convective motions, which for observed pulsars lead to an almost so-angular-momentum rotation law with ω ∼ 1/R 2 inside the shell. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instabilities while taking cooling into account. The settling regime of accretion is possible for moderate accretion ratesṀ Ṁ * ≃ 4 × 10 16 g/s. At higher accretion rates a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of spin-up/spin-down rates of quasi-spherically wind accreting equilibrium X-ray pulsars with known orbital periods (like e.g. GX 301-2 and Vela X-1), it is possible to determine the main dimensionless parameters of the model, as well as to estimate the magnetic field on the surface of the neutron star. For equilibrium pulsars with independent measurements of the magnetic field, the model also allows us to estimate the velocity of the stellar wind from the companion without the use of complicated spectroscopic measurements. For non-equilibrium pulsars, it can be shown that there exists a maximum possible value of the spin-down rate of the accreting neutron star. From observations of the spin-down rate and the X-ray luminosity in such pulsars (e. g. GX 1+4, SXP 1062 and 4U 2206+54) we are able to estimate a lower limit on the neutron star magnetic field, which in all exemplified cases turns out to be close to the standard one and in agreement with cyclotron line measurements. The model further explains both the spin-up/spin-down of the pulsar frequency on large time-scales and the irregular short-term frequency fluctuations, which may correlate or anti-correlate with the X-ray luminosity fluctuations, seen in different systems.

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Section: Discussionmentioning

confidence: 61%

Section: The Alfvén Surfacementioning

confidence: 99%

Section: Spin-up and Spin-down Of X-ray Pulsarsmentioning

confidence: 99%

See 1 more Smart Citation

Quasispherical subsonic accretion in X-ray pulsars

Шакура¹,

Постнов²,

Kochetkova³

et al. 2013

Phys.-Usp.

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“…Several methods of magnetic field estimation in X-ray pulsars were applied by Chashkina & Popov (2012). Among them the authors used a new model of quasi-spherical accretion by Shakura et al (2012).…”

Section: High-mass X-ray Binaries and Ns Evolutionmentioning

confidence: 99%

Unifying neutron stars getting to GUNS

2014

Self Cite

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The variety of the observational appearance of young isolated neutron stars must find an explanation in the framework of some unifying approach. Nowadays it is believed that such scenario must include magnetic field decay, the possibility of magnetic field emergence on a time scale of 10 4 -10 5 yr, significant contribution of non-dipolar fields, and appropriate initial parameter distributions. We present our results on the initial spin period distribution, and suggest that inconsistencies between distributions derived by different methods for samples with different average ages can uncover field decay or/and emerging field. We describe a new method to probe the magnetic field decay in normal pulsars. The method is a modified pulsar current approach, where we study pulsar flow along the line of increasing characteristic age for constant field. Our calculations, performed with this method, can be fitted with an exponential decay for ages in the range of 8×10 4 -3.5×105 yr with a time scale of ∼ 5×10 5 yr. We discuss several issues related to the unifying scenario. At first, we note that the dichotomy, among local thermally emitting neutron stars, between normal pulsars and the Magnificent Seven remains unexplained. Then we discuss the role of high-mass X-ray binaries in the unification of neutron star evolution. We note, that such systems allow to check evolutionary effects on a time scale longer than what can be probed with normal pulsars alone. We conclude with a brief discussion of the importance of discovering old neutron stars accreting from the interstellar medium.

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“…Only the Kluzniak and Rappaport and the Ghosh and Lamb models takeṖ into account, with the other models assuming spin equilibrium. For more details see [11] and for spin equilibrium methods see also [19].…”

Section: Magnetic Fieldsmentioning

confidence: 99%

Spin period change and the magnetic fields of neutron stars in Be X-ray binaries in the SMC

Klus

Coe

et al. 2014

EPJ Web of Conferences

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Abstract. We report on the long term average spin period, rate of change of spin period and X-ray luminosity during outbursts for 42 Be X-ray binary systems in the Small Magellanic Cloud. We also collect and calculate parameters of each system and use this data to determine that all systems contain a neutron star which is accreting via a disc, rather than a wind, and that if these neutron stars are near spin equilibrium, then over half of them, including all with spin periods over about 100 seconds, have magnetic fields over the quantum critical level of 4.4×10 13 G. If these neutron stars are not close to spin equilibrium, then their magnetic fields are inferred to be much lower, on the order of 10 6 -10 10 G, comparable to the fields of neutron stars in low mass X-ray binaries. Both results are unexpected and have implications for the rate of magnetic field decay and the isolated neutron star population.

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Magnetic field estimates for accreting neutron stars in massive binary systems and models of magnetic field decay

Cited by 36 publications

References 50 publications

Quasispherical subsonic accretion in X-ray pulsars

Quasispherical subsonic accretion in X-ray pulsars

Unifying neutron stars getting to GUNS

Spin period change and the magnetic fields of neutron stars in Be X-ray binaries in the SMC

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